This invention relates to photography and more particularly, to novel photosensitive photographic elements, particularly novel photosensitive emulsions.
As a result of the known disadvantages of gelatin, in particular, its variable photographic properties and its fixed physical properties, for example, its diffusion characteristics; much effort has been expended in the past in order to replace gelatin with a suitable synthetic grain-growing protective colloid for photographic silver halide emulsions. Many synthetic polymeric materials have heretofore been suggested as peptizers for silver halide emulsions, however, these have generally not functioned satisfactorily and frequently have not fulfilled all of the basic requirements for a photosensitive silver halide emulsion grain-growing protective colloid listed following:
(1) ABSENT (OR CONSTANT) PHOTOGRAPHIC ACTIVITY;
(2) ABILITY TO FORM AN ADSORPTION LAYER ON MICROCRYSTALS OF SILVER HALIDE PERMITTING STABLE SUSPENSIONS TO BE OBTAINED;
(3) ABILITY TO FORM ADSORPTION LAYERS AS DESCRIBED IN (2) ABOVE WHICH DO NOT PREVENT GROWTH OF SILVER HALIDE MICROCRYSTALS DURING PHYSICAL RIPENING; AND
(4) SOLUBILITY IN WATER SOLUTION.
In addition, hithertofore, much emphasis has been placed on the ability of the synthetic polymeric material to mix with gelatin, as this property has been critical for employment in partial substitution reactions with gelatin. Consequently, many synthetic polymers of the prior art have been materials which allow for the growth of silver halide crystals only in the presence of gelatin.
Polymeric materials having cyanoacetate units, i.e., --OCOCH.sub.2 CN, are known to be useful in photographic compositions, as shown by Smith, U.S. Pat. No. 3,554,987; Smith British Pat. No. 1,215,610; Beavers, U.S. Pat. No. 3,576,628; and Unruh et al, U.S. Pat. No. 2,808,331. These polymers are clearly different from the polymers of the instant invention since the cyanoacetate appendage of the former is affixed to an alkylene chain through an O atom, whereas the cyanoalkyl acrylate appendage of the present polymers is affixed to the polymeric backbone through a C atom. Similarly, French Pat. No. 1,588,198 describes photographic elements comprising copolymers of vinyl alcohol and cyanoethyl vinyl ether, whose cyanoalkyl appendages are affixed to the polymeric backbone through the ether O atom. Polymers or copolymers of acrylonitrile have been described in the art as being useful additives to photographic silver halide emulsions, (e.g., see British Pat. No. 1,215,610 and Japanese Pat. No. 21448/71); however, it has been hithertofore unknown to employ the cyanoalkyl acrylate polymers and copolymers described herein as binders for said silver halide emulsions.